Wyniki wyszukiwania - BazTech

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Badania doświadczalne wpływu włókien hybrydowych na zachowanie się belek żelbetowych przy zginaniu

Shanthi Vengadeshwari R., Jagannatha Reddy H.N., Prabhakara R.

Cement Wapno Beton

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2022

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R. 27, nr 1

59--70

PL

Dodatek włókien jest obiecującym rozwiązaniem, poprawiającym zachowanie belek żelbetowych przy zginaniu. Wpływa na poprawę właściwości tych belek w zakresie obciążenia szczytowego, plastyczności i absorpcji energii. Nieefektywne włókna mono w betonie działają bardzo efektywnie, gdy są połączone poprzez hybrydyzację i przyczyniają się do zwiększenia wytrzymałości. Hybrydyzacja włókien zapewnia poprawę właściwości mieszanki betonowej i stwardniałego betonu. Dla zapewnienia optymalnych właściwości użytkowych ważniejszy jest synergiczny efekt włókien. Wprowadzenie dwóch rodzajów włókien do matrycy betonowej skutecznie mostkuje rysy. W celu zbadania wpływu hybrydyzacji włókien na zginanie, przygotowano belki żelbetowe, przeprowadzono doświadczenia i porównano wyniki z belkami kontrolnymi. W niniejszej pracy zamierzano ocenić i porównać wpływ włókien stalowych i bazaltowych, w postaci mono i hybrydowej, na przebieg zginania, a mianowicie pierwsze obciążenie przy pęknięciu, zachowanie się pod wpływem obciążenia, plastyczność, szerokość pęknięcia i wytrzymałość na zginanie belek żelbetowych. Do oceny właściwości mechanicznych betonu zbrojonego włóknami klasy M40, wybrano udziały objętościowe włókien wynoszące 0,25%, 0,5% i 0,75%. Połączenie włókien bazaltowych z włóknami stalowymi, w znacznym stopniu poprawia właściwości poprzez synergię działania. Na podstawie ogólnej oceny właściwości mechanicznych ustalono, że połączenie włókien bazaltowych i stalowych w ilości odpowiednio 0,25% i 0,75%, dało najlepsze wyniki. Optymalne udziały objętościowe tych włókien zastosowano do wykonania belek. Tam, gdzie było to możliwe, wyniki prób zginania były weryfikowane z normami indyjskimi.

EN

Addition of fiber is a promising solution, to enhance the flexural behaviour of reinforced cement concrete [RCC] beams. It improves the peak load, ductility and energy absorption characteristics of RCC. Ineffective mono fibers in the concrete perform very effective, when combined through the hybridization and contribute towards the strength. Fiber hybridization offers appreciable improvement in fresh and hardened properties of concrete. To achieve optimum performance, synergetic effect of fibers is more important. Incorporation of two fibers in concrete matrix, bridges the cracks effectively. Hence to investigate the effect fiber hybridization in the flexural performance, RCC beams were cast, experimented and the results were compared with the control beams. In the present study, it is intended to evaluate and compare the impact of steel and basalt fibers in mono form and hybrid form, on the flexural parameters such as first crack load, load response behaviour, ductility, crack width and flexural strength of RCC beams. To evaluate the mechanical properties of M40 grade fiber reinforced concrete, volume fractions chosen were 0.25%, 0.5% and 0.75%.Comparatively addition of basalt fibers with steel fibers, improves synergetic response to a considerable extent. From overall assessment of the mechanical properties, it was established that the combination of basalt and steel fibers at 0.25% and 0.75% respectively, produced optimum results. Optimum volume fraction of fibers identified is used in the casting of RCC beams. Wherever possible, flexural parameters were cross checked, with Indian Standards.

2

Mechanical Effects on Different Solid to Liquid Ratio of Geopolymer Filler in Epoxy Resin

Abu Hashim Mohammad Firdaus, Ghazali Che Mohd Ruzaidi, Daud Yusrina Mat, Faris Meor Ahmad, Al Bakri Abdullah Mohd Mustafa, Zainal Farah Farhana, Hasyim Saloma, Lokman Muhammad Taqiyuddin

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 1

215--220

EN

Geopolymer is formed from the alkali activation of materials rich in Si and Al content with the addition of a silicate solution to enhance the properties of the materials. This paper presents research on the mechanical properties of fly ash-based geopolymer filler in epoxy resin by varying different solid to liquid ratios using sodium hydroxide and sodium silicate as the alkaline activator. However, the common problem observed from the solid to liquid ratio is the influence of curing time and compressive strength of geopolymer to have the best mechanical property. The mix design for geopolymers of solid to liquid ratio is essential in developing the geopolymer’s mechanical strength. A series of epoxy filled with fly ash-based geopolymer materials with different solid to liquid ratio, which is prepared from 0.5 to 2.5 solid to liquid ratio of alkaline activator. The tensile strength and flexural strength of the epoxy filled with fly ash-based geopolymer materials is determined using Universal Testing Machine under tensile and flexural mode. It was found that the optimum solid to liquid ratio is 2.0, with the optimum tensile and flexural strength value. However, both the tensile and flexural properties of epoxy filled with fly ash-based geopolymer suddenly decrease at a 2.5 solid to liquid ratio. The strength is increasing with the increasing solid to liquid ratio sample of geopolymer filler content.

3

Reliability - based analysis of the flexural strength of concrete beams reinforced with hybrid BFRP and steel rebars

Zhang Wei, Liu Xiang, Huang Yiqun, Tong Ming-Na

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 4

art. no. e171, 2022

EN

The durability of reinforced concrete structures has always been an important problem in civil engineering because steel rebars rust easily. Therefore, fiber-reinforced polymer (FRP) rebars possessing good corrosion resistance, low weight, and easy construction has become a substitute for reinforcement. However, since FRP rebar has a low elastic modulus and is a brittle failure material, large deflections and cracks occur in the FRP concrete beam with no obvious warning before failure. A hybrid reinforced concrete beam that combines the advantages of steel rebar and FRP rebar is a good structural form. The reliability of hybrid reinforced beams must be analyzed to ensure their safety. A flexural performance test of the hybrid basalt FRP (BFRP)–steel-reinforced beam was performed, the failure mode was explored, and the numerical models were established. The accuracy of the models was verified by comparing them with the test results. The numerical models were used to establish a database (630 cases) that was combined with existing research results (33 cases), to obtain the statistics of the uncertainty of the prediction model. Reliability analysis of a large-scale design space was conducted to calibrate the BFRP. Finally, the average deviation from the target reliability index suggested that the values of the partial coefficient of the materials range from 1.2 to 1.4.

4

Influence of untreated abaca fibre on mechanical properties of lightweight foamed concrete

Othuman Mydin Md Azree

Architecture Civil Engineering Environment

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2022

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Vol. 15, no. 3

51--61

EN

Presently, the expenditure on construction materials grows dramatically along with the enduring effect on the ecosystem, and it has led the academics to the recognition of natural plant fibres such as abaca fibre (AF) for enhancing the mechanical properties of concrete. AF is plentifully obtainable making it fairly relevant to be employed as a strengthening material in lightweight foamed concrete (LFC). Moreover, natural plant fibre-reinforced concrete has been progressively utilized in construction for several decades to decrease crack growth under the static load. This paper anticipates examining the effectiveness of the addition of AF in LFC to enhance its mechanical properties. LFC specimens of 550 kg/m3 density were reinforced with AF at weight fractions of 0.00%, 0.15%, 0.30%, 0.45% and 0.60%. Three parameters have been assessed which were flexural strength, compressive strength and tensile strength. The results revealed that adding 0.45% AF into LFC enables optimal compressive, flexural and splitting tensile strengths. The presence of AF augments material strength by filling spaces, micro-cracks, and gaps inside the LFC structure. Additionally, AF helped reduce crack spreading when the plastic state of the LFC cementitious matrix was loaded. Though, further, than the optimum level of AF addition, accumulation and the non-uniform distribution of AF were identified, which triggers the lowering of the LFC strength properties substantially. The output of this preliminary investigation would give a better understanding of the potential utilization of plant fibre in LFC. It is of great importance to drive the sustainable development and application of LFC material and infrastructures.

5

Utilization of wrightia tinctoria nano seed fibers as a reinforcement in the preparation of epoxy-based composites

Syed Habibunnisa, Nerella Ruben, Madduru Sri Rama Chand, Reddy S Raja Gopal

Acta Innovations

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2022

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no. 45

5--17

EN

Natural seed fiber reinforced composite materials are replacing many conventional ones because of their excellent properties, less weight, easy availability, etc. Composite materials are used in many areas because of their superior features. Mechanical property is one of the vital parameters for choosing the material. The current investigation has revealed an importance of recently well-known Wrightia tinctoria nano seed fibers (WTNSFs), which are extracted physically. Wrightia tinctoria nano seed fiber reinforced composite was prepared with the epoxy resin by hand layup method. Epoxy resin is easy to handle and available at low cost. Mechanical tests are conducted reinforced composites of plain epoxy and WTNSFs to obtain strength properties like tensile, flexural, impact. Water absorption tests also performed on composites. Here, the developed composites are easy to handle, offered economically, and used primarily in marine applications due to less water absorption and good wax content. A comprehensive description of different tests and the properties of WTNSFs are studied and compared with the other existing natural fibers. This work showed that 35% combination of WTNSFs reinforced epoxy matrix offers enhanced mechanical properties with minimum water absorption compared with plain epoxy composites.

6

Experimental investigations on concrete beams reinforced with equivalent service steel pipe

Al-Yassri Labeeb S., Al-Ramahee Munaf A., Al-Khekani Alaa M.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2021

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Vol. 30, No. 1

16--28

EN

Different techniques were employed for the passage of different utilities through structural elements. The reduction of the overall building weight was the main concern that needs to be achieved, especially for a multistory building. It can be done with the eliminating of a suspended ceiling with a portion of the beam’s weight by taking the advantages of the hollow sections. In this study, an equivalent reinforcement to the traditional ribbed reinforcement was employed to fabricate a reinforced concrete (RC) beam with a hollow section along the length of the beam. A steel pipe was used based on the equivalent moment from section analysis. Two diameters were selected of steel pipes as an equivalent to the commercial reinforcement. A total of four RC beams were cast and tested, two of them with traditional reinforcement and the other with steel pipe reinforcement. The comparison showed a promising result in terms of ductility, cracking pattern, ultimate strength, and mode of failure compared to the reference beam. The peak loads for the specimens with steel pipe were 160.6 kN and 184 kN, while they were 192 kN and 203.5 kN for the beams with traditional reinforcement.

7

Mechanical properties of kenaf fiber thermoplastic polyurethane-natural rubber composites

Noor Azammi A. M., Sapuan S. M., Ishak M. R., Sultan M. T. H.

Polimery

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2018

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T. 63, nr 7-8

524--530

EN

Thermoplastic polyurethane-natural rubber TPUR-NR composites filled with treated and untreated kenaf fiber as filler were prepared at different TPUR and NR contents. The content of kenaf fiber was maintained at 12.5 wt % and the fiber was treated with 6 % solution of sodium hydroxide (NaOH), then dried for 24 hours in 100 °C, hot blended with polymer components, pulverized and pressed. The mechanical properties of the composites such as tensile, flexural and impact strength were determined, and their dependence on NaOH treatment of kenaf fibers was investigated. The analysis using scanning electron microscope (SEM) was implemented to identify the effect of alkali treatment on the microstructure of kenaf fiber and TPUR-NR composites. An improvement of fiber surface roughness and bonding between the fiber and polymer as well as an increase in impact energy and elongation at break of the composites was observed.

PL

Otrzymano kompozyty na osnowie termoplastycznego poliuretanu (TPUR) i naturalnego kauczuku (NR) (o różnej zawartości TPUR i NR), napełnionej włóknami kenafu KF (12,5% mas.). Włókna poddawano wstępnej obróbce przy użyciu 6% roztworu wodorotlenku sodu, suszono w temp. 100 °C przez 24 h, mieszano na gorąco z komponentami polimerowymi, pulweryzowano i prasowano. Zbadano właściwości mechaniczne przy ściskaniu i rozciąganiu oraz odporność na uderzenie kompozytów zawierających modyfikowane lub niemodyfikowane włókna kenafu, a także wpływ alkalicznej obróbki włókien na właściwości kompozytu. Obserwacje mikrostruktury kompozytów prowadzono metodą skaningowej mikroskopii elektronowej. Stwierdzono, że obróbka włókien KF roztworem NaOH wpłynęła na zwiększenie chropowatości ich powierzchni i zdolności wiązania z osnową polimerową, a także na poprawę odporności na uderzenie i zwiększenie wydłużenia przy zerwaniu kompozytów zawierających modyfikowane włókna.